Thirteen United States Senators have written a letter to the U.S. Ambassador to the U.N., Nikki Haley, asking for tougher inspections of Iranian sites and better reporting by the International Atomic Energy Agency, IAEA about the implementation of the 2015 nuclear deal, JCPOA.

Senator David Perdue’s (R-GA) official website has published the text of the letter, in which the senators question why IAEA does not have access to all relevant sites in Iran, especially military ones.

“When unveiling the JCPOA, President Obama promised that, ‘inspectors will also be able to access any suspicious location. Put simply, the organization responsible for the inspections, the IAEA, will have access where necessary, when necessary.’ He stressed that Iran’s nuclear program ‘faces strict limitations and is subject to the most intrusive inspection and verification program ever negotiated to monitor a nuclear program.’ In practice, it appears that this is not the case,” wrote the senators.

The letter cites Iranian officials who said recently that Iran’s military sites are “off limits” and they “will never allow such visits.”

They ask Ambassador Haley to work with her counterparts at the U.N. to resolve these issues.

Senators Ted Cruz and Marco Rubio are among the signatories of the letter.

Among other issues the senators mention is uncertainty among the signatories of the JCPOA regarding the boundaries of what constitutes activities "which could contribute to the design and development of a nuclear explosive device." They quote IAEA Director Yukiya Amano saying that "more clarification would be helpful".

Amano is scheduled to visit Iran on Saturday, October 28.

The letter also asks improved IAEA reporting on uranium mining, conversion and enrichment.